GiftCard options sort order is wrong on MySQL 8

• GiftCard options for specified amount should be sorted by by price ASC

• saas-expoty may return data as is, but SF API should provide correct sort order

• test fixed and unskipped in Magento\GiftCardProductDataExporter\Test\Integration\GiftCardProductTest::testGiftCardFixedAmountMultipleWebsites

Additionally:

• rename rendertype "giftcardopenamount" to "giftcard_openamount"
• for Specified Giftcard Amount:
  • add price to option value (productOptions.values.price field)
  • cover changes with tests (see  Magento\GiftCardProductDataExporter\Test\Integration\GiftCardProductTest::testGiftCardFixedAmountMultipleWebsites)
  • rename rendertype "drop_down" to "giftcardamount"

Test failed: 

PR: #403